Polyvinylidene fluoride (PVDF) as anode and cathode binder for lithium batteries

Polyvinylidene fluoride (PVDF) is a kind of polymer material, which has good chemical stability and machinability, and plays a positive role in improving the bonding performance. It is widely used in lithium-ion batteries as a positive and negative binder.
The main factors affecting the adhesion of PVDF are molecular weight, crystallinity, PVDF modification, cathode material and conductive agent. The larger the molecular weight of PVDF is, the stronger the adhesion is, and the higher the peeling strength of the electrode is. The higher the crystallinity is, the closer the molecular chains are, the greater the intermolecular force is, and the better the adhesion is.
The solubility of PVDF in solvent is mainly affected by crystallinity, particle size, molecular weight, polarity and dissolution temperature. In addition to the dissolution of PVDF powder, the water content of NMP solvent should be specially controlled. The water absorption degree of NMP is more serious than that of positive active material, conductive agent and other materials. It is easy to attack the pH value of the adjacent molecules of nmc-h and dfc-h in the slurry. The increase of the number of double bonds will cause the viscosity of the slurry to increase. When it is serious, it will produce gel like jelly, which can not be properly coated.